Lubricating metal foil



April 2, 1935. 'r. A. TORRENCE El' AL 1,995,392

LUBRICATi NG METAL FOIL Filed Sept. 5, 19:50

REW/ND 6 50056655 nous INVENTORS ZATORRE/VCE BY ATTORNEYS ELEND EA/V Patented Apr. 2, 1935 LUBRICATING IVIETAL FOIL Thomas A. Torrence, Parnassus, and Frank L.

Endean, Pine Manor, Pa., assignors to Aluminum Company of America, Pittsburgh, Pa., a I corporation ofPennsylvania Application September 5, 1930, Serial No. 479,940

29 Claims.

This invention relates to metal foil, particularly aluminum foil, having novel surface qualities and improved working characteristics.

Foil, as the term isused herein and in the appended claims, is a convenient designation of a class of metal products, in sheet form, which are of comparatively light gauge. The invention as herein described comprehends sheet aluminum of a wide range of thickness, and the term foil is used to designate such aluminum products as a class and not as limited to sheet of extremely light gauge. Such aluminum products, or foil, are used for many purposes which require that the foil after being rolled into sheet form be formed by dies or by pressing or drawing into various shapes of both simple and intricate design.

When the aluminum foil is placed in the die or similar forming mechanism or in a machine such as a cutting machine, it is very often found that the surface of the foil coming in contact with the different metal of the die produces a frictional force between the two metal surfaces which so seriously interferes with the working of the metal that satisfactory operation is not obtainable. This frictional force is suflicient to cause tearing and/or wrinkling of the foil in the working mechanism, or uneven working effects in different portions of the article even when such portions are subjected to equal working forces. Such frictional forces are particularly obnoxious in their effects when the metal is of very light gauge and cannot withstand the tensional and shearing stresses which metal of heavier gauge is capable of withstanding.

Moreover, when foil sheets are piled flat one upon the other the sheets can not be readily removed from such a pile, because of the frictional forces existing between the metal surfaces, especially when the contacting surfaces are highly polished, as they are in many cases. These and other instances where friction between metal surfaces is present have caused great difliculty in the proper handling and/or working of foil sheets. While the solution of such problems appears to lie in proper lubrication, there has been no lubricant proposed or used here ofore, so far as we have been able to ascertain, which will satisfactorily meet the ofttimes rigorous requirements as to cleanliness and appearance as well as lubricating efliciency.

It is accordingly an object of this invention to provide lubricants which will satisfactorily overcome the above mentioned difficulties. A further object is the provision of a foil having thereon a permanent, invisible and clean lubricant which.

will reduce substantially the friction of the foil surface with the surface of the same or other metal. Another object of the invention is the provision of a foil which when submitted to working operations will not tear or wrinkle during 5 such operations. Another object is to provide an effective method of applying the lubricant to the foil sheets. To these and other ends the invention comprises the novel process and product hereinafter described.

Wehave discovered, as a result of extensive tests, that certain members of the chemical compounds usually known as the fatty acids and having the general formula CnH2no2 have lubricating qualities highly useful in substantially reducing the aforementioned friction, and that they combine with these exceptional lubricating qualities other desirable characteristics which overcome the difficulties heretofore encountered in the lubrication of foil surfaces.

The members of that class of compounds known as the fatty acids which we have found to be suitable for the purposes above described are thoseof the general formula CnH-znOz where n is greater than 10. The compounds containing less than 10 carbon atoms and 20 hydrogen atoms are not adapted to our purposes because they do not meet one of the principal requirements of a suitable foil lubricant, viz., a lubricating film which, while preventing substantial friction, is nevertheless hard, dry, and non-greasy.

The provision on the foil of a permanent lubricating film which presents a hard, dry surface is an important aspect of our invention. Heretofore one of the principal difliculties of obtaining a proper foil lubricant has been the greasy nature of the lubricating substance and its propensity to soil and/or contaminate the material ,with which it comes in contact. Since these light gauge metal products are formed into containers and coverings for foods, teas, spices and edible liquids or are used as decorative containers for these and other substancesit is imperative that any lubricant present on the metal be non-greasy and non-toxic in nature and also odorless or at any rate inoffensive to the olfactory organs. All of these conditions are met by the use of our lubricants without sacrifice of the reduction in frictional resistance which is the principal reason for lubricant application; Also because of these qualities the fatty acids which we have described need not be removed from the foil after the form-' ing operation but may remain thereon without prejudicial effect. I Whileany; of the fatty acids of the general formula CnH2nO2 (where n is greater than 10) may be used as a foil lubricant in accordance with our invention, we have found that certain of such acids are particularly useful. In practicing our invention with aluminum foil, in connection with which our invention is especially advantageous, we found that the fatty acids of the general formula CnHznOz in which n is 12 to-l4 inclusive, and especially those in which n is 16 to" 18 inclusive, are to be preferred because of their remarkable lubricating properties. They are,

. also, easily obtained commercially. Thus we prefer to use palmitic acid (C16H32O2) or stearic acid (C18H3602) or the mixture of these acids conveniently obtained in the form of stearin, a common article of commerce. The fatty acid lubricants may be applied to the foil by any of several methods but we have obtained the best results by preparing a solution of the fatty acid lubricant in a volatile solvent and spreading this solution uni-- formly over the foil surface by immersing the metal in the solution and thereafter passing the moistened metal through rolls to distribute the solution evenly and remove any excess. The foil may then be allowed to remain in the air until the volatile solvent, in which the fatty acid is dissolved, evaporates, but we have preferred to hasten such evaporation by passing the metal, as it issues from the solution in which it is immersed, over a heated drum. The drying drum, however, should not be too strongly heated since too great a heat will destroy the lubricating film which is deposited as the solvent evaporates. In preparing a solution for the purpose any solvent which volatilizes readily and does not leave a noticeable or objectionable residue may be used. Examples of such solvents are benzol, alcohols, and the like. The amount of the fatty acid present in the solution should be sufficient to leave, on evaporation of the solvent, a substantial lubricating film on the metal foil. The thickness and effectiveness of this film may be increased by adjusting the concentration of fatty acid present in the solution. Where stearin is used as the lubricant we have discovered that a-solution containing as little as 0.2 per cent by weight will produce on aluminum foil a lubricating film answering many requirements, but where the working operation to which the aluminum foil will be later subjected is severe, a solution containing as much as 10 to 15 per cent of stearin may be desirable. As above mentioned, the properties of the lubricating film of fatty acid placed on the metal foil in accordance with our invention are seriously impaired when the metal foil is heated to high temperatures and, for this reason, it is desirable to apply the fatty acid to the foil after the annealing operation if, as in the case of aluminum foil, it is at times necessary to anneal the metal at comparatively high temperatures.

Foil, coated with a hard, dry fihn of a fatty acid of the general formula CnHBnOZ (where n is greater than 10) has, in. addition to the many properties and advantages above mentioned, a pleasing surface lustre or color which is somewhat softer in appearance than the surface lustre of unlubricated foil. This pleasing lustre is particularly desirable because of the many decorative uses to which such foil is put.

The advantages of foil coated with a film of fatty acid in accordance with the principles of our invention may be well illustrated by a specific example of the use of aluminum foil coated with stearin. In the manufacture of caps or seals for milk bottles from aluminum foil it is necessary, because of low cost requirements and the large numbers of such caps required, to use automatic machinery which, operating at high speed, successively stamps from a strip of foil a cap-shaped seal or cap of the size and shape desired. The speed of this operation requiresthat the formed metal articles be ejected rapidly from the stamping die and that stamping take placewithout tearing or wrinkling of the metal. Prior to our invention, it was necessary, because of the high frictional resistance existing between the aluminum foil and the steel die, to lubricate the metal at the time of stamping with oil or similar liquid lubricant. The subsequent use of the articles on milk or other edible product containers necessitated the removal of the lubricant after the forming operation, which removal involved considerable expense. However, aluminum foil coated with stearin in accordance with our invention and thereby provided with a permanent, hard, dry, lubricating film, inoffensive in appearance and free from toxic effects, may be employed in such rapid stamping operations without further lubrication and with very little waste by tearing or wrinkling of the metal.

In the accompanying drawing we have illustrated diagrammatically a simple and eifective apparatus for applying the lubricant to the foil.

In the drawing, I is a receptacle containing the coating solution, into which the foil H is led from a supply roll l2, passing under the roll l3 which is partially submerged in the solution. From the roll l3 the foil, now carrying on each side a liquid film of the solution, passes between squeegee rolls l4, l5, which serve tospread or distribute the films evenly and reduce the same to a uniform thickness. From the squeegee rolls the foil passes over the drying drum l6 (which may be internally heated in any convenient manner) and thence between guide rolls l1, l8 to the takeup or rewind roll 19. Any convenient driving mechanism may be used, and mechanisms suitable for the purpose are well known.

It is to be understood that the invention is not limited to the features herein specifically described but can be carried out in other ways without departure from its spirit.

We claim- 1. As an article of manufacture, a metallic foil having a permanent lubricating coating of a compound having the general formula CnH2n02 where n is greater than 10.

2. As an article of manufacture, a metallic foil having a permanent lubricating coating of a compound having the general formula CnHZnOZ where n has a value between 16 and 18 inclusive.

3. As an article of manufacture, a metallic foil having a permanent lubricating coating of stearin.

4. As an article of manufacture, a metallic foil having a permanent lubricating coating of a mixture of palmitic and stearic acids.

5. As an article of manufacture, a metallic foil having a permanent lubricating coating oi palmitic acid.

6. As an article of manufacture, a metallic foil having a permanent lubricating coating of stearic acid.

'7. A metallic foil having on its surface a hard, dry, lubricating coating of a compound of the general formula CnHZnOZ (where n is greater than and capable of being easily formed in a die without further lubrication.

8. Aluminum foil having on its surface a hard,

consisting ofavolatilesolvent and stearic acid.

dry, lubricating coating of a compound of the general formula CnH2nO2 (where n is greater than 10') and capable of being easily formed in a die without further lubrication.

9. A metallic foil having on its surface a hard, dry, lubricating coating of a compound of the general formula CnH2no2 (where n is 12 to .14 inclusive) and capable of being easil in-a die without further lubrication.

10. Aluminum foil having on its surface a hard, dry, lubricating coating of a compound of the general formula CnHznOz (where n is 12 to 14 inclusive) and capable of being easily formed in a die without further lubrication.

11. A metallic foil having on its surface a hard; dry, lubricating coating of stearin and capable of being easily formed in a die without further lubrication.

12. Aluminum foil having on its surface a hard, dry, lubricating coating of stearin and capable of being easily formed in a die without further lubrication.

13. In a method of lubricating aluminum foil, the step comprising placing on the foil a volatile solvent containing in solution a compound having the general formula CnHznOz where n is greater than 10.

14. In a method of lubricating aluminum foil, the step comprising placing on the foil a volatile solvent containing in solution a compound having the general formula CnHZnOZ where n is 16 to 18 inclusive.

15. In a method of lubricating aluminum foil, the step comprising placing on the foil a volatile solvent containing one or more of the fatty acids having the general formula CnH2nO2 where .n is greater than 10. I

16. In a method of lubricating alumium foil, the step comprising placing on the foil a volatile solvent containing one or more of the fatty acids having the general formula CnHanOz where n is 12 to 14 inclusive.

1'7. In a method of lubricating aluminum foil, the step comprising placing on the foil a'volatile solvent containing stearin.

18. In a method of lubricating aluminum foil, the step comprising placing on the foil a volatile solvent containing a mixture of palmitic acid and stearic acid.

19. In a method of lubricating aluminum foil, the step comprising placing on the foil a solution consisting of a volatile solvent and palmitic acid.

' 20. In a method of lubricating aluminum foil," the step comprising placing on the foil a solution 21. In a method of lubricating aluminum foil, the step comprising placing on the foil a solution consisting of a volatile solvent and one or more of the compounds of the general formula CnH2n02 where n is greater than 10.

22. In a method of lubricating aluminum foil, the steps comprising passing a continuous strip of the foil through a solution of the lubricant to coat the foil therewith, and thereafter passing the foil through rolls to remove the excess solution and over a heated drum.

23, In a method of lubricating al of the foil through a solution of the lubricant to coat the foil therewith, and thereafter passing the foil successively between distributor rolls and over a heated drying drum.

24. In a method of lubricating aluminum foil, the steps comprising passing a continuous strip of the foil through a volatile solvent containing in solution a compound having the general formula CnHZnOii where n is between 16 and 18 inclusive,

and thereafter passing the foil through distributor rolls and over a heated drying drum.

25. In a method of lubricating aluminum foil, the steps comprising unwinding the metal through a s tearic acid solution and rewinding over a heated drum.

26. In a method'of lubricating aluminum foil,

the steps comprising passing a continuous strip of the foil through a solution of stearic and palmitic acids, thereafter passing the foil over a heated drum to evaporate the solvent in which the said acids are dissolved.

27. As an article of manufacture, metallic foil for use in the manufacture of covers for milk bottles and edibles-and which has a permanent and clean lubricating coating inocuous to milk and other edibles with which the coating may come into contact, said coating consisting of a hard and dry compound of the class of compounds known as fatty acids and having the general formula CnHznOZ where n is greater than 10.

28. As an article of manufacture, aluminum foil for use in the manufacture of milk bottle closures and containers for edibles, said aluminum foil having a coating of a hard, dry film of a fatty acid having the general formula CnHflnOZ (where n is. greater than 10) for lubricating the foil during its manufacture into bottle closures or containers, said film being suitable for contact with foil, g y formed the stepscomprising passing a continuous strip food stuffs without contaminating, soiling, or'

otherwise undesirably affecting the. same.

29. As an article of manufacture, aluminum 7' dry, non-greasy, non-toxic, and inocuous to milk and other edibles with which the coating may come into contact.

THOMAS A. TORRENCE. 

